Composite plug door for use on railcars

ABSTRACT

Composite doors are described which include a frame defining at least two openings and at least two composite panels situated within the openings in the frame. Preferred uses for such composite doors are as plug doors for use on railcars.

BACKGROUND OF THE INVENTION

Railcars are used generally for transporting goods and are equipped in many cases with doors known as “plug” doors. These doors slide open, generally on a track and by using a cranking mechanism for accessing the interior of the railcar. Such doors are traditionally known to be made of the same type of material as the railcar, i.e., steel. While such doors are strong and resilient, they pose certain disadvantages in that they are very heavy adding weight to the overall railcar weight and making them difficult to operate. Further, they are subject to corrosion under exposure to the elements.

As a result, attempts have been made in the art to improve such doors. One such design includes a door in which the inner and outer portions of the door are formed of fiberglass-reinforced epoxy skins over an aluminum honeycomb-patterned core. The core is bonded to the skin with voids in the structure being plugged by insulation. A panel in the center of the door opens to allow access to the crank rod door opening mechanism.

Another prior art attempt to improve upon steel hatch doors includes a railcar which is formed of a sandwich-like composite. These doors (unlike most plug doors) open by raising and close by lowering. By using the composite, only one hatch door is needed instead of several metal hatch doors. The door is made more structurally stable than prior art composite hatch doors by including a balsa wood core.

In addition to trying to use fiberglass reinforced plastic substitutes for steel in metallic railcar doors, metallic doors for boxcars are also known in which the doors include separate modular metallic sections so that if the door is dented, the modular panel can be replaced. The metallic panels in such doors include elastomeric or other flexible materials between panels and an outer heavier gauge metallic frame so that the sections can move and bend on impact.

Entire railcars, including their plug doors, have been proposed in which the entire structure is formed of a foam core or wood reinforced thermosetting or thermoplastic material in one large molded railcar that sits on a frame. Such cars are lighter weight than metallic cars and more corrosion-resistant. The doors are also lighter if formed of the reinforced plastic material. In addition, I-beams can be incorporated in foam blocks in the core within the sidewalls of the railcar.

An alternative solution to rendering railcars lighter in weight is to form the framing of a railcar of a composite sandwich laminate. Such laminates have outer cover layers of fiber laminate material, between which may be a honeycomb core and frame.

While there have been prior art attempts, such as those described above, to make a lighter weight, more user-friendly railcar and/or railcar door, there is a need in the art for railcar plug doors which contribute to decreasing the overall weight of the railcar while maintaining the structural integrity of the railcar door, decreasing corrosion issues, allowing for ease of use by the operator and allowing easy repair in the event of damage to the car. It would also be advantageous to provide such a door with improved appearance, lower repair costs, and which includes sufficient structural integrity in addition to lowering weight so as to resist collapse that could cause injury, decrease wear and load on components to reduce maintenance while allowing for reduction in overall fuel and operating costs.

BRIEF SUMMARY OF THE INVENTION

The invention includes a composite door comprising a frame defining at least two openings and at least two composite panels situated within the openings in the frame. In a preferred embodiment, the composite door is a plug door suitable for use as a railcar plug door.

The invention also includes a railcar plug door comprising an outer frame configured to define an outer periphery of the plug door and an inner frame configured to fit within the outer frame, the inner frame defining at least two openings and at least two composite panels situated within the openings in the inner frame.

A method for forming a plug door, comprising forming an outer frame defining an outer periphery of the plug door; forming an inner frame configured to fit within the outer frame, wherein the inner frame defines at least two openings; securing the inner frame within the outer frame; and placing a composite panel within each of the at least two openings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

In the drawings:

FIG. 1 is a front elevational view of a railcar plug door according to an embodiment described herein;

FIG. 2 is a front elevational view of an outer frame which can be used according to an embodiment of the plug door described herein;

FIG. 3 is a cross-sectional view of a portion of the outer frame of FIG. 2 taken along line D-D of FIG. 2;

FIG. 4 is a front elevational view of an inner frame for use in an embodiment of a plug door as described herein;

FIG. 5 is a cross-sectional view of a portion of the inner frame in FIG. 4 taken along line E-E;

FIG. 6 is a front elevational view of lattice closure frame for closure of the inner frame of FIG. 5;

FIG. 7 is a cross sectional view of the lattice of FIG. 6 taken along lines F-F;

FIG. 8 is a front elevational view of two composite panels for use in a frame in accordance with an embodiment of the plug door described herein;

FIG. 9 is a cross sectional view of a portion of one of the composite panels of FIG. 8 taken along line C-C;

FIG. 10 is a cross-sectional view of a portion of the plug door of FIG. 1 taken along line A-A; and

FIG. 11 is cross-sectional view of a portion of the plug door of FIG. 1 taken along line B-B.

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenience only and is not limiting. The words “lower” and “upper” and “top” and “bottom” designate directions in the drawings to which reference is made. The terminology includes the words above specifically mentioned, derivatives thereof and words of similar import.

Referring now to the drawings in detail, there is shown in FIG. 1 an embodiment of a plug door in accordance with a preferred embodiment, referred to generally as 10. It should be understood based on this disclosure that the embodiment as shown herein is a preferred embodiment for best illustrating the invention and that the invention should not be considered to be limited thereby. The door has a frame 12 that includes an outer frame 14 and, as shown in FIGS. 1 and 2 and an inner frame 16 as shown in FIGS. 1, 4 and 6. The frame 12, and more preferably the inner frame has at least two openings 18 as shown in FIG. 4. Preferably, there is a plurality of such openings within the frame. Because the frame and composite panels can be made of varying sizes and varying numbers of panels for different uses (even beyond the preferred use as a traditional railcar plug door), it should be understood based on this disclosure that the invention is not fixed by the preferred frame arrangement shown in FIGS. 1, 2, 4 and 6.

In preparing a preferred railcar plug door according to one preferred embodiment of the invention, it was intended that the door have a load capability which was approximately equivalent to that of current steel railcar plug doors for 2, 3 and 4 psi loads uniformly distributed over the door surface. The door should perform comparably to such a steel door in the free-to-roll mode when an empty car is impacted with a coupler force of 1,250,000 lbs. It was also desirable that the door work in the same dimensional environment and be able to be used with the same mountings and operating mechanisms as current steel doors. The operating environment was also targeted to include conditions from 40° F to 150° F. It was also preferred that the composite door be able to be formed using conventional thermoforming techniques. With respect to stiffness, the panels are preferred to have a stiffness that approximates that of current steel doors.

The outer frame 14, as best shown in FIGS. 1 and 2 is preferably configured to define an outer periphery P of the plug door. The inner frame 16 is preferably configured to fit within the outer frame 14. The fit need not be exact in terms of a facing engagement between parts, however, it is preferred as discussed further herein that there be some form of sealing to render the door water tight and/or insulative for railcar and other similar uses. The inner and outer frames can be formed as one complete structure either formed as a one-piece unit out of metal such as stainless steel, iron, aluminum or other metals or alloys as well as formed from a suitable polymeric, plastic and/or composite material having sufficient reinforcing strength to support the overall structure 10. Alternatively, the inner and outer frames can be made integrally out of interlocking pieces. In addition, while the frame 12 is illustrated herein as being formed of an inner and outer frame which are separate pieces, it should be understood to be within the scope of this disclosure to make a one-piece frame (encompassing both the inner and outer frames) which is a unitary part, perhaps of welded metal or molded plastic or other composite of sufficient strength. The one- and two-piece frames may use fasteners of varying types to facilitate installation and replacement of the panels, when necessary. Other techniques such as, but not limited to “H” channels and “U” channels may also be used for this purpose. In addition, it should be understood that while conventionally shaped sections such as “T,” “C,” “H” and “U” channel pieces may be used in the invention, framing and other sections may be formed of custom-designed configurations as well to form the frame sections in order to optimize weight to stiffness ratio.

However, it is preferred that, as shown in FIGS. 1, 2, 4, 5, 10 and 11, the outer frame 14 is formed as one portion of the door and the inner frame 16 is formed as a separate structure. As shown in FIG. 2, the outer frame 14 preferably is formed so as to have four side sections 20 which may form a generally rectangular structure, with the understanding that other shapes are also possible (generally square, triangular, circular or other polygonal shape). The side sections can each be a single flat piece, angle iron, a “C”- or “U”-channel, a “T”- channel, plate, two joined “L”-channels or combinations thereof as well as other various configurations of raw metallic stock or other suitable material or custom designed to optimize properties as noted above. Use of such raw metallic material stock is preferred because it is inexpensive and readily available. However, it should be understood from this disclosure that any configuration of sufficient structural strength which provides an outer frame capable of supporting and securing or being formed in conjunction with an inner frame as described herein is within the scope of this disclosure. FIG. 3 shows that in cross-section, the side sections 20 are preferably formed of “L”-channels which can be of variable length and are preferably also adjustably and removably fastened together by any acceptable fastening mechanism, such as a joint, lock, snap-in configuration, clips, adhesives, bolt, screw, etc. In FIG. 3, two “L”-channels 22 are shown bolted together by bolt 24 so that in cross-section the two “L”'s are facing one another to form an overall generally rectangular open “U” configuration as shown. By bolting (or otherwise fastening) two separate pieces, the frame can be made adjustable in size (in depth) and/or the frame can be more easily assembled and dismantled if desired and/or more easily repaired in the event damage is sustained to one surface. Further, in constructing the plug door 10, by having two independent pieces along a side, the outer frame can be assembled prior to or after the assembly of the inner frame.

If the door as shown is to be used as a typical plug door for a railcar, the outer frame 14 preferably has two opposing side sections 20 that are about 130 inches (330 cm) to about 140 inches (356 cm) in length, preferably about 110 inches (279 cm) to 120 inches (305 cm), and most preferably they are about 120 inches (305 cm) in length as measured parallel to the longitudinal axis L-L of each side section on the longer sides of the frame as shown in FIG. 2. The door would also have two other opposing side sections 20 that are about 130 inches (330 cm) to about 140 inches (356 cm) in length, preferably from about 110 inches (279 cm) to about 120 inches (305 cm), and most preferably about 120 inches (305 cm) in length as measured parallel to the longitudinal axis L′-L′ of each of those side sections as shown in FIG. 2. In such an embodiment, the “L”-channel is preferably about 1.25 inches (3.18 cm) to about 1.50 inches (3.81 cm), and most preferably about 1.5 inches (3.8 cm) measured longitudinally along either leg of the “L”, and the “L” channels are preferably about 0.19 inches (0.48 cm) to about 0.32 inches (0.81 cm) and most preferably about 0.25 inches (0.64 cm) in thickness, as measured transversely in cross section across either leg of the “L”. Exemplary bolts for use and as shown are preferably ½-13 bolts located generally centrally between the two “L”-channels and preferably are evenly spaced along the frame sections 20. Generally about 64 such bolts would be suggested for a typical sized railcar plug door of 144 inches×120 inches as preferred herein, but the number and spacing of such bolts may vary in such an embodiment and in other configurations of the door as described herein. Of course, if the door were formed of a unitary piece or different material, bolts or other fasteners could be optional. The corners where each of the side sections 20 meet are preferably also welded or otherwise fastened together. For a railcar plug door of typical size, there are about twelve such welds. It should be understood based on this disclosure that while suitable dimensions are being provided for the example of a typical railcar plug door for purposes of illustrating an example of the invention, the dimensions can be varied and altered for different doors for varied uses and/or various sized railcars.

The inner frame according to the invention defines at least two openings and is configured so as to receive and secure at least two composite panels, one in each of the opening. Likewise, at least two composite panels are provided to the structure and are correspondingly configured so as to fit within the openings in the inner frame. The fit need not be in full facing engagement or completely side to side such that some flexibility can be built into the structure, however, if the door is to be water tight or insulative, it is preferred that there be a weld (metallic or polymeric) or other sealing method used to seal where the composite panels fit within the frame. The composite panels preferably fit within the inner frame so as to create a tongue-in-groove configuration with the inner and outer frames as shown, for example, as shown in the Figures herein (see, e.g. FIGS. 10 and 11).

The inner frame may also be formed of any of the various types of raw metallic stock described above for the outer frame or a suitable material of roughly equivalent structural integrity as mentioned above. However, preferably the inner frame 16 is formed of a lattice-like structure of various intersecting beams 26, 30 as best shown in FIG. 4. Preferably, such beams are each “T” beams and the beams can fit within the outer frame to define an overall frame which defines at least two openings 18 as shown in FIG. 4 where the outer frame is shown in phantom lines. Preferably, for a railcar plug door, a plurality of such openings can be defined by the intersecting beams of the inner frame and/or the outer frame and such beams. Each “T”-beam is preferably, but need not necessarily be, of a similar dimension to the metallic stock portions used to form the outer frame. For example, if 1.5 in. “L”-channels are used for the outer frame, then “T” channels of about 1.5 in. (3.8 cm) are preferably used for the inner frame such that the sizes are compatible and the inner frame is configured to fit within the outer frame. Preferably, the base 32 and the top 34 of the “T” are the same size, but that need not be the case. As shown in a typical plug door according to a preferred embodiment herein, in FIGS. 4 and 5, the inner frame is preferably formed of 1.5 in (3.8 cm) “T”-channels which form a lattice that is configured to fit within the outer frame so that the frame defines eighteen (18) openings 18.

It is preferred that if the inner frame is not one pre-formed section, and is made of intersecting beams, that those beams are fastened together for structural stability. As shown in FIG. 4, for a typical railcar plug door according to a preferred embodiment of the invention, horizontally extending, longer-sized beams 26 are welded or otherwise joined to smaller sections 30 of vertically extending beams at intersecting areas. As shown in FIG. 4, and working within the preferred illustration of a 144 in.×120 in. railcar plug door configuration, each longer beam 26 is preferably about 116 inches (295 cm) in length as measured along the longitudinal axis A-A of each of such beams. The shorter beams 30 extending vertically in FIG. 4 would then be preferably about 22.1 inches (56.1 cm) in length as measured along the longitudinal axis A′-A′ (about 23.6 inches (60 cm) as measured from the base 32 of each “T”). The shorter, vertically extending beams 30 can be spaced at varying distances from each other horizontally and the longer, horizontally extending beams 26 can be spaced from each other varying distances from each other vertically to create differing effects, different sized openings or varied appearances for the composite panels that are configured to fit within the openings. As shown in FIG. 4, in a preferred railcar plug door embodiment, the beams 30 are spaced so that they are about 37.1 inches (94.2 cm) apart (about 38.6 inches (98 cm) as measured horizontally along longitudinal axis A-A between the bases 32 of each “T”). A composite panel configured to fit within the opening, preferably snuggly, should, but need not, extend between the base 32 of each “T” beam in the interlocking inner frame so that for the composite panels (and respective openings) the preferred dimensions would be about 37.5 inches (121 cm) by about 23 inches (58.4 cm). However, as noted above, the dimensions may be varied from the preferred embodiment depending on the design and intended use of the door. Similarly, as noted above, standard frame or “A” and “T” beams need not be used and custom designed pieces may be substituted provided they can secure panels within the inner frame as described herein.

Preferably, to better secure the composite panels within the inner frame, a separate, lattice 36 as shown in FIG. 6 is preferably provided to the plug door. While lattice 36 is preferred for additional security, the composite panels may be otherwise secured within the inner frame. If an additional lattice such as lattice 36 is provided, it preferably has dimensions that correspond to the dimensions of the inner frame 16. The cross-section of such lattice 36 preferably is configured so as to provide a counter surface on the opposite side of the composite panel from the “T” or other configuration used to form the inner frame as best shown in FIG. 11. Preferably, the cross-section of the lattice 36 is either formed of flat plate, “C”-channel or other suitable raw stock material as shown in FIG. 11, however, it may be formed of other suitable materials as noted hereinabove. In the preferred embodiment used for purposes of illustration, a preferred “C”-channel as shown in FIG. 7 could be of a size that is about 1.5 inches (3.8 cm) along its base and about 0.56 inch (1.42 cm) on either shorter leg 37 of the “C”. The “C”-channel is preferably about 0.19 inches (0.48 cm) in thickness, however, the size and configuration of the “C”-channel or other lattice piece (like other portions of the inner frame, may vary in size and thickness). In order to secure the lattice 36 in place in the plug door 10, fasteners, adhesives, clips and/or sealants may be used to connect and/or attach the lattice to the inner frame. As shown in FIG. 6, welds or similar joining mechanisms or fasteners may be used to attach shorter vertical pieces 38 to the longer horizontal pieces 40. Bolts or other fasteners may be located near the edges and at the intersections of the vertical and horizontal pieces 38, 40 of the lattice. In the preferred embodiment shown, there are about 68, ½-13 bolts located as shown, however, more or less such fasteners may be used, and if the lattice is of a one-piece unitary construction, fasteners may be optional.

The composite panels for use in the invention preferably include an interior reinforcing core and an outer skin or skins of thermoformable or other suitable material such as thermosetting plastics, plywood or other materials, preferably, however, it is thermoformable material. The outer skin may, for example, be molded around the core as a single layer which coats the entire core or may be formed of two separate skins of the same or different thermoformable or other suitable material that are then joined along their periphery using various techniques, such as, for example, heat bonding or similar polymer welding or joining techniques or directly forming or bonding the skins to the panel using adhesives or heat fusion, for example. Alternatively, the entire structure can be reinforced thermoformable material and the core can be optional. It should be understood that the basic nature of the panels can be varied within the scope of the invention.

If a core is provided between outer skin layers, the core can be any suitable core material that is capable of providing the desired strengthening properties. Preferably, the core material is of a generally lower mass material than the outer skins. Exemplary core materials include aluminum rod, honeycomb (which may be aluminum or plastic honeycomb), balsa wood, plywood or combinations thereof. Most preferred as a core material is a honeycomb aluminum core of about 0.5 inch (1.3 cm) that is generally formed of a thickness of about 0.55 inches (1.4 cm) from aluminum of about 0.02 inch (0.05 cm) thickness. The preferred weight for such material is about 0.66 lb/in² at the specified thickness.

The skin material, as noted above may be formed of a wide variety of materials as noted above. If formed of thermoformable material, it may be any suitable heat moldable plastic, and preferably thermoplastic material, including polyolefin (polypropylene and polyethylenes and their copolymers), polystyrenes and other polymeric dienes and butadienes (such as polyacrylonitrile-butadiene-styrene), polycarbonates, polyarylene ethers (such as PEEK, PEK and PEKK), polyurethanes, polyimides and polyetherimides. Additionally, grafted, random and block copolymers of such materials may also be used to optimize physical properties for different uses of the doors of the invention. Most preferably an inexpensive, easily moldable material such as a polyolefin, and more preferably a polyethylene is used. In the preferred railcar plug door embodiment, the most preferred thermoformable material is high density polyethylene (HDPE).

The thermoformable materials noted above for use may also include any of a variety of molding additives known in the art or to be developed for adjusting the properties of the plastic for preferred uses, including plasticizers, stabilizers, UV absorbers, flame retardants, fillers, reinforcing fibers, particles or whiskers, conductive fillers for charge dissipation, rheological or wear-resistant additives and the like.

Exemplary molded composite panels are shown, for example in FIGS. 8 and 9. In FIG. 8, the panels are molded so as to exhibit a design showing crossed reinforcing ribs 44 (also shown in FIG. 1). The ribs are optional, and corrugations or other designs may be used as desired, and the panels may also optionally be flat or have patterns, logos or other designs or written information embossed in their exterior. FIG. 9 shows a cross-sectional view of a portion of an exemplary panel having an aluminum honeycomb core material. In its thickest portion as shown, the thickness is about 1.3 inches (3.3 cm) and at its narrowest thickness, it is about 1.05 inches (2.67 cm). The outer skin surrounding the core as shown as about 0.12 inches (0.31 cm) in thickness on either side of the core. However, it should be understood based on this disclosure that the thicknesses of the core, the outer skins and the corresponding frame can be varied for different thickness doors and to provide doors of varying sizes, design configurations and properties.

Exemplary preferred composite railcar plug door panels made according to the invention having 2 ft×3 ft (61 cm×91 cm) dimensions and a skin of high density polyethylene of about 0.02 inch (0.05 cm) in thickness over an aluminum 5052, 0.5 inch (1.27 cm) web with 0.0025 inch (0.0064 cm) foil at 0.55 inch (1.40 cm) thick, deflected 0.192 in. (0.488 cm) in thickness when subjected to a load of 2 psi pressure. This compares with prior art steel panels of the same dimension and 0.375 inch (0.953 cm) thickness, which under the same load deflect about 0.2 inch (0.508 cm). However, in comparing the overall weight of a door formed according to the preferred embodiment described herein with steel inner and outer frame and HDPE composite, lower-density core panels as noted herein, for a 10 ft.×12 ft.×1.3 inch (305 cm×366 cm×3.3 cm) thick ribbed composite door there is about 270 pounds of plastic and composite, 492 pounds of steel for a total weight of 762 pounds. A steel door of dimensions 10 ft.×12 ft.×0.375 inch (305 cm×366 cm×0.953 cm) weighs comparatively 1836 pounds. Thus, the advantages of the present invention can be seen, in which the composite panels and design of the composite doors significantly reduce the weight of the door while retaining the deflection and stiffness characteristics and ability to operate in similar environmental conditions.

Other advantages of the composite doors of the invention include no painting requirements for the panels, which are easily replaced (as are portions of the inner and outer frames), and no rusting of panels. Easy repair and/or inexpensive partial replacements of portions of the door as opposed to the entire door. Ability to address flammability through acceptable flame retardant additives. Due to the lower weight, there is less risk of the door falling from its intended position, reducing the risk of injury and less wear and load on door components and mechanisms, further reducing maintenance requirements. The doors also can be made to have improved aesthetic appearances and improved durability, since there is no rusting on panels and no need to re-paint.

In a preferred embodiment, gaps and spaces within the overall door structure should be sealed or otherwise filled. However, if insulation or sealing of the plug door is not an issue, this may be an optional feature of the invention. A material may be provided between the frame and the various composite panels, wherein the material is selected from a sealant, a flexible structure, caulking or combinations thereof. As shown in FIGS. 10 and 11, sealant may be placed between the composite doors 42 and the outer frame 14 along portions of the “L” pieces 22 and can be placed around the entire periphery or only a portion or portions thereof. In FIG. 11, sealant 39 is illustrated as being placed on either side of the composite panels 42 between the panels and the inner frame 14 along one of the “T”'s 32 and between the panels 42 and the lattice 36.

For additional security, the panels may also be further secured by placing fasteners for holding the composite panels within the openings in the frame in various locations. In addition, strength support and security may be provided by adding at least one cross brace (not shown) across the entire door structure for additional support to the plug door within the frame 12.

It should also be understood that a plug door according to the invention may be operated using any acceptable crank or other door operating mechanism, including other hardware such as existing locks, levers, rollers and the like which are known in the art or to be developed.

The invention also includes a method for forming a plug door. The method includes forming an outer frame defining an outer periphery of the plug door, forming an inner frame configured to fit within the outer frame, wherein the inner frame defines at least two openings; securing the inner frame within the outer frame; and placing a composite panel within each of the at least two openings. The outer frame and inner frame used in the method may be those frame portions described above with respect to plug door 10 and may be two independently formed structures, or, as noted above, formed as one unitary structure. The inner frame should be configured so as to have at least two openings such as openings 18 within the frame.

The frame should is preferably secured so as to place the inner frame within the outer frame and securing the two together such as by a fastener system, for example, the bolts described above. A further lattice such as lattice 36 may then be placed on the opposite side of the panels from the inner frame for additional security.

The composite panels in the method are preferably formed of one or two outer skins of any of the suitable materials discussed above, including thermoformable materials. The outer skin(s) may be formed by separately extruding each skin or by coextruding two skins around a central core, or by directly applying skins to a core such as by heat fusion, adhesives or any other suitable techniques. If the outer skins are separately formed, then can be bonded either adhesively or thermally around their outer periphery to seal the skins. If a core is used, the core is preferably positioned within the skins before sealing them. The outer skins after extrusion, if formed of thermoformable materials, can also be thermoformed into a desired shape of the composite panels for various effects (such as the panels having a “cross” design as shown in FIG. 1) prior to sealing the outer skins around any core reinforcing material or the panels may be heat stamped or molded to have such as design after the panel is formed.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims. 

1. A composite door comprising: a frame defining at least two openings and at least two composite panels situated within the openings in the frame.
 2. The composite door according to claim 1, wherein the frame comprises an outer frame and an inner frame.
 3. The composite door according to claim 2, wherein the outer frame is configured to define an outer periphery of the composite door.
 4. The composite door according to claim 2, wherein the inner frame is configured to fit within the outer frame.
 5. The composite door according to claim 2, wherein the outer frame is configured to define an outer periphery of the composite door and the inner frame is configured to fit within the outer frame.
 6. The composite door according to claim 5, wherein the inner frame defines the at least two openings and is further configured to receive and secure the at least two composite panels within the openings and said at least two composite panels are configured so as to fit within the openings.
 7. The composite door according to claim 6, wherein the composite panels fit within the inner frame in a tongue-in-groove configuration.
 8. The composite door according to claim 5, wherein the outer periphery and the outer frame are generally rectangular in shape.
 9. The composite door according to claim 5, wherein the outer frame comprises portions which are formed of raw metallic stock selected from the group consisting of angle iron, “C”-channel, “T”-flange, plate or combinations thereof.
 10. The composite door according to claim 9, wherein the outer frame portions are connected by at least one of welding and fasteners.
 11. The composite door according to claim 1, wherein the composite panels comprise an interior reinforcing core and outer skins of thermoformable material.
 12. The composite door according to claim 11, wherein the interior reinforcing core comprises aluminum, honeycomb, balsa wood, plywood or a combination thereof.
 13. The composite door according to claim 11, wherein the thermoformable material is a polyolefin.
 14. The composite door according to claim 13, wherein the polyolefin is a high density polyethylene.
 15. The composite door according to claim 1, wherein the frame defines a plurality of openings and there are a corresponding plurality of composite panels.
 16. The composite door according to claim 1, further comprising a material between the frame and the composite panels, wherein the material is selected from a sealant, a flexible structure, caulking or combinations thereof.
 17. The composite door according to claim 1, further comprising fasteners for holding the composite panels within the openings in the frame.
 18. The composite door according to claim 1, wherein the door is a plug door.
 19. The composite door according to claim 18, wherein the plug door is a railcar plug door.
 20. A railcar plug door comprising: an outer frame configured to define an outer periphery of the plug door and an inner frame configured to fit within the outer frame, the inner frame defining at least two openings and at least two composite panels situated within the openings in the inner frame.
 21. The railcar plug door according to claim 20, wherein there are a plurality of openings in the inner frame and a plurality of the composite panels.
 22. A method for forming a plug door, comprising forming an outer frame defining an outer periphery of the plug door; forming an inner frame configured to fit within the outer frame, wherein the inner frame defines at least two openings; securing the inner frame within the outer frame; and placing a composite panel within each of the at least two openings.
 23. The method according to claim 22, further comprising forming the composite panels by forming two outer skins of a thermoformable material, thermoforming the outer skins into a desired shape of the composite panels and sealing the outer skins around a core reinforcing material. 